Command line parameters

  • papadopoulosa

    papadopoulosa - 2014-02-10

    I am having a horrendous time trying to figure out the parameters in 7-zip command line. I am running on Win7Pro, 16GB RAM, Quad i7. Here is a sample command line I am using:

    7z a -t7z -mx3 -v4450m -m0=lzma2:d20 -mmt2 -slp "guest" "V:\VMs\guest"

    The command is running the source directory. Here is what I understand and what I don't understand:

    -mx3 light to medium compression
    -v4450m split output file size to about DVD size
    cannot find what -m0 is all about; help file does not show a -m9 parameter (which I can find)
    Understand lzma2 and d20 is a 20MB dictionary size (I used to use 24, but read that 20 gives faster compression in the forum)
    -mmt2 run with two threads
    -slp enables large pages

    Can someone help me understand what the -m0xxx command does, or point me to the section in the docs I am missing?

    Thank you very much
    For a great program

  • Igor Pavlov

    Igor Pavlov - 2014-02-11

    look in -m switch help:
    {N}={MethodID}[:param1][:param2] ... [:paramN]
    -mx3 means fast
    d20 means 1 MB dictionary (2^20).

  • papadopoulosa

    papadopoulosa - 2014-02-11

    Thank you for the reply sir. I still don't understand what the -m0 implies. I have seen examples where the show multiple versions of this parameter, i.e. -m0 -m1 -m2.

  • gdv22

    gdv22 - 2014-03-09

    @ papadopoulos a

    I'm just trying to understand these switches myself, so I'm not sure I've got this right, but from examples in the -m (Set compression Method) switch section of CHM help file, it appears to me that:

    • -m0 is simply the first {MethodID} specified,
    • -m1 is the second {MethodID} specified, and
    • -m2 is the third {MethodID} specified a multiple method (3 in this case) compression specification.

    Does that seem right? ...and if so, does it help with your question?

    Last edit: gdv22 2014-03-09

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